stock_list = [['招商银行',0.0124],['兴业银行',0.0111],
            ['中国银行',-0.0078],['宁波银行',0.0036]]
inner_f = lambda x: [x[0], float(x[1])]
stock_map = map(inner_f, stock_list)
print(type(stock_map))
stock_list = list(stock_map)
print(stock_list)